1. Field of the Invention
The present invention relates to a camera with an imaging-element unit that has an imaging element for obtaining image signals corresponding to the light applied to its photoelectric conversion surface. The invention relates to, for example, an improvement to a camera such as a single-lens reflex, digital camera in which lenses can be replaced.
2. Description of the Related Art
In recent years, digital cameras and the like (hereinafter called “digital cameras” or “cameras”), such as so-called digital still cameras and so-called digital video cameras, have come into general and wide use. The digital cameras have the following structure.
In the digital camera, the light beam reflected from an object and passing through the optical system (hereinafter referred to as “object light beam”) defines an image of the object. The image of the object is focused on the photoelectric conversion surface of a solid-state imaging element or the like that is arranged at a prescribed position. The solid-state imaging element is, for example, a charge coupled device (CCD, hereinafter referred to as “imaging element”). The imaging element performs photoelectric conversion, generating an electric image signal that represents a desired image of the object.
A signal based on the image signal is output to a display device such as a liquid crystal display (LCD). The display device displays the image that corresponds to the image signal. The image signal generated by the imaging element is recorded as image data in a predetermined region of a specific recording medium. The image data recorded in the recording medium is read and converted to image data that is optimal for the display device to display the image. Using the image signal thus converted, the display device displays the image corresponding to the signal.
Ordinary digital cameras have an optical finder device. Through the finder device the user observes a desired object in order to set a photographing field in which the object is seen, before he or she take a picture of the object.
The optical finder device is configured as follows. When the user views the object, the reflecting member is located on the optical axis of the photographing optical system. Thus located, the reflecting member reflects the object light beam. The object light beam is guided to a predetermined position, where an image of the object is formed so that the user may observe it. To photograph the object, the reflecting member is moved away from the optical axis of the photographing optical system. As a result, the object light beam is guided to the light-receiving surface of the imaging element, or the photoelectric conversion surface. An image of the object, which is to be photographed, is thereby formed on the photoelectric conversion surface. The finder device of this configuration is called “single-lens reflex type” and is generally used.
In recent years, digital cameras have come into general use. They comprise a finder device of the single-lens reflex type and whose photographing optical system can be removed from the camera body. With a digital camera of this type, the user can replace the lenses with others. The user can therefore use any selected one of various types of photographing optical systems, in the same camera body.
In the case of such a lens-replaceable digital camera, dust and the like floating in air may enter the camera body when the photographing optical system is removed from the camera body. The camera body contains a shutter mechanism, a diaphragm mechanism and the like, which are mechanically driven. When driven, these mechanisms may form dust in some cases.
When the photographing optical system is removed from the camera body, the light-receiving surface (also called “photoelectric conversion surface”) of the imaging element, which is arranged at the back of the photographing optical system, is exposed to air in the camera body. Dust may therefore stick onto the photoelectric conversion surface of the imaging element due to electrical charging or the like.
There has been proposed the technique that inhibits dust and the like from sticking to the light-receiving surface of the imaging element used in a conventional single-lens reflex digital camera, despite electrical charging. Such a technique is disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 2000-29132.
The technique disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2000-29132 is to provide a transparent electrode on the cover that covers the light-receiving surface of the imaging element that is incorporated in a lens-replaceable, single-lens reflex digital camera. A DC voltage or AC voltage of about several kilohertz to 20 kHz is applied to this electrode, thereby to prevent dust and the like from sticking to the light-receiving surface of the imaging element, in spite of electrical charging.
According to the publication, the electric charge generated in the imaging element is neutralized to inhibit dust and the like from sticking to the light-receiving surface of the imaging element, despite static electricity.
Most imaging elements widely used in the conventional digital cameras are elements that are sealed in packages (called “packaged CCDs” for example). In recent years it has been proposed that so-called “bare-chip CCDs,” or bare CCD chips, be supplied to the market, along with the packaged imaging elements.
Dust and the like are more likely to stick to the photoelectric-conversion surface of the bare-chip CCD. In view of this, it is proposed that a piezoelectric element be interposed between the bare-chip CCD and the substrate supporting the bare-chip CCD. A voltage is applied to the piezoelectric element, vibrating the bare-chip CCD and causing the dust and the like to fall off the bare-chip CCD. This technique is disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 9-130654.
The applicant hereof has filed Japanese Patent Application No. 2000-401291. In the application, the applicant proposes that a dust-shielding member and a vibrating means be provided. The dust-shielding member covers and protects the photoelectric conversion surface of an imaging element, thus inhibiting dust and like from sticking to the photoelectric conversion surface of the imaging element. The vibrating means vibrates the dust-shielding member to make dust and the like fall from the dust-shielding member.
This technique can inhibit dust and the like from sticking to the photoelectric conversion surface of an imaging element by the use of a small and simple mechanism. The technique can also provide a lens-replaceable digital camera in which dust and the like can be easily removed from the dust-shielding member.
Particles of the dust and the like that stick to the surface of the dust-shielding member varies in side and weight. Thus, the dust-shielding member is vibrated not only in a single mode, but also in various modes by changing vibration frequency and amplitude, thereby removing the dust and the like with higher efficiency.